• Nie Znaleziono Wyników

Data fusion solutions to compute performance measures for urban arterials

N/A
N/A
Info
Pobierz
Protected

Academic year: 2021

Share "Data fusion solutions to compute performance measures for urban arterials"

Copied!
16
0
0

Ładowanie.... (Zobacz pełny tekst teraz)

Pobierz teraz ( 16 Stron )

Pełen tekst

(1)

8/13/14

Symposium Celebrating 50 Years of Traffic Flow Theory

2014 TFT Summer Meeting

August 11-13, Portland, Oregon USA

Data fusion solution to fix the cumulative drift

problem on urban arterials

(2)

Context

•

 

In the Netherlands

•

 

Virtually 100% vehicle actuated

traffic controllers: inductive

loops measuring flows (and in)

•

 

Last five years: huge

investments in urban

monitoring, particularly in AVI

systems (cams, BT)

•

 

TRAVEL TIMES

•

 

REALISED ROUTES

•

 

PARTIAL OD RELATIONS

•

 

Usefulness for urban traffic

management debated …

(3)

Overview

1.

 

Deducing vehicle accumulation using vehicle counts (cum

curves) is straightforward …

2.

 

Problem: cumulative drift due to errors in counts

3.

 

Solution: (f)use counts (with) measured travel times

(4)

t

2

t (time)

n (vehicles)

N(t) = n

1

-n

2

n

2

n

1

n

1th

vehicle

TT(t)= t

2

-t

1

t

1

Cross section x

1

•  Flow: q

(veh/u)

Cross section x

2

•  Flow: q

(veh/u)

Q

1

(t)

d

dt

Q

1

(t)

= q

1

(t)

Q

2

(t)

d

dt

Q

2

(t)

= q

2

(t)

(5)

The cumulative drift problem

•

 

Source errors (miscounts, double counts):

•

 

lane changes, power failure, etc.

•

 

Errors may be random or structural (bias)

•

 

Consequence:

With e.g.

Occurs when q

1

(t) and q

2

(t) contain errors

N (t)

= q

1

(s) ds

t

∫

− q

2

(s) ds

t

∫

q

i

(t)

= ˆq

i

(t)

+

ε

i

(t)

⎫

⎬

⎪

⎭

⎪

N (t)

= ˆN(t) +

∫

t

(

ε

1

(s)

−

ε

2

(s)

)

ds

ε

i

(t) ~ N (

µ,σ )

(6)

The cumulative drift problem

•

 

Source errors (miscounts, double counts):

•

 

lane changes, power failure, etc.

•

 

Errors may be random or structural (bias)

•

 

Consequence:

Occurs when q

1

(t) and q

2

(t) contain errors

N (t)

= q

1

(s) ds

t

∫

− q

2

(s) ds

t

∫

q

i

(t)

= ˆq

i

(t)

+

ε

i

(t)

⎫

⎬

⎪

⎭

⎪

N (t)

= ˆN(t) +

∫

t

(

ε

1

(s)

−

ε

2

(s)

)

ds

This is a random walk!

(which means vehicle accumulation is

practically unobservable using counts)

(7)
(8)

t

2

t (time)

n (vehicles)

n

2

t

1

Q

1

(t)

Q

2

(t)

raw da

ta

raw data

TT

!

r

(t

2

)

Solution

n

0

t

0

(9)

t

2

t (time)

n (vehicles)

n

2

t

1

Q

1

(t)

Q

2

(t)

raw da

ta

raw data

n

1

TT

!

r

(t

2

)

TT

r obs

(t

2

)

ε

TT

(t

2

)

Solution

Implies we either

•  Underestimated inflow

•  Overestimated outflow

•  Or both

n

0

t

0

(10)

t

2

t (time)

n (vehicles)

n

2

t

1

Q

1

(t)

Q

2

(t)

corre

cted

raw da

ta

raw data

n

1

Correction factor

is proportional to

ε

TT

TT

!

r

(t

2

)

TT

r obs

(t

2

)

ε

TT

(t

2

)

Solution

n

0

t

0

(11)

TT

!

r

(t

2

)

TT

r obs

(t

2

)

ε

TT

(t

2

)

n

2

n (vehicles)

t

2

Q

1

(t)

Q

2

(t)

t

0

=

Q

2

(t

2

)

n

0

t (time)

t

*

= Q

1 −1

(n

2

)

Q

1

*

(t)

Full weight

Inflow

Q

1

(t

1

)

→ Q

1 *

(t

1

)

ε

N

(t

2

)

Q

2

*

(t)

Full weight

outflow

Q

2

(t

2

)

→ Q

2 *

(t

2

)

ε

N

(t

2

)

t

2

− TT

r obs

(t

2

)

(12)

Solution turns out to be

•

 

Correction factor can be expressed

as function of known quantities only

•

 

Or more generally

A simple parameter-free correction algorithm

ε

N

(t

2

)

ε

TT

(t

2

)

=

n

2

− n

0

t

*

− t

0

ε

N

(t

i

)

=

ε

TT

(t

i

)

Q

i

(t

i

)

− n

0

Q

i

−1

−1

(n

i

)

− Q

i

−1

−1

(n

0

)

(13)

Results

Rows (random errors): {1%, 5%, 10%}

Columns (bias):

{-5%, 0, 5%};

(14)

Results

Rows (random errors): {1%, 5%, 10%}

Columns (bias):

{-5%, 0, 5%};

(15)

Discussion

•

 

Good news for urban traffic management agencies:

•

 

Algorithm works offline or online (although with a time lag of course)

•

 

Quite a few puzzles to solve:

•

 

Limits algorithm (magnitude and nature of errors)

•

 

What to do when no closed counting situation?

•

 

What to do when no measured travel times?

(16)

Next steps …

•

 

Solve puzzles

•

 

Pubs:

•

 

TRB2015 paper:

•

 

Basic idea + extension to multiple links

•

 

TFT50 / special issue jnl paper

•

 

Basics TRB Paper

•

 

+ combination with additional methods

Cytaty

Pobierz teraz ( PDF - 16 Stron - 2.50 MB )

Powiązane dokumenty

Kopalne nasiona winorośli w osadach limnicznych Ostrowa Lednickiego

Jacquat i Martinoli, po analizie kilkuset kopalnych pe­ stek winorośli z Petry w Jordanie i testowaniu kilku powszechnych metod ich identy­ fikacji, konkludują że odróżnienie

Jan Baudouin de Courtenay a carska cenzura

i obrońcy — przypominając, że Baudouin de Courtenay wywodzi się od Ludwika IX, że jego przodkowie brali udział w wyprawach krzyżowych, stwierdza z emfazą:

Multigrid Method for the Coupled Free Fluid Flow and Porous Media System

The multigrid method - an efficient numerical technique for solving sys- tems of linear and nonlinear equations - is employed for the solution of the discretized poroelastic

Photogeneration and Mobility of Charge Carriers in Atomically Thin Colloidal InSe Nanosheets Probed by Ultrafast Terahertz Spectroscopy

We have determined the photogeneration charge carrier quantum yield and mobility in atomically thin colloidal InSe nanosheets (inorganic layer thickness 0.8 – 1.7

Antoni Gaudi, een weg tot oorspronkelijkheid

Daar naar mijn bevinding noch in de ontwerpen voor de Coöperatie te Mataró en Casa Vicens, noch in de tekening voor het jachtpaviljoen enig element voorkomt van de

Павел филонов - "Очевидец незримого" : из истории худошецтвенного авангарда в России

Невзирая на провозглашение самим Филоновым ряда прогрессивных художественных и педагогических принципов, которые, по мысли

Dzieje parafii unickiej w Pienianach

przy cerkwi w Pienianach widnieje zapis, że potrzebuje „reperacji we wszyst- kich częściach”, świątynia w Hopkiem „reperacji we wszystkich częściach” i tylko